Regulated high-voltage power supply



Feb. 27, 1951 A. E. HUDSON 2,543,632

REGULATED HIGH-VOLTAGE POWER SUPLY Filed Dec. 16, 1949 Inventor-c Aligancier E1. Hudson, b filo 451m 9 His Attornek Patented Feb. 27, 1951 2,543,832 anoum'rsn HIGH-VOLTAGE rowan SUPPLY Alexander E. Hudson, ,Albany, N. Y., assignor to General Electric Company, a corporation of New York Application December 16, 1949, Serial No. 133,278

' 3 Claims. 1

My invention relates to regulated high voltage direct current power supplies, and particularly to such power supplies incorporating a radio frequency oscillator.

An object of my invention is to provide an improved regulated high voltage direct current power supply.

A more specific object of my invention is to provide effective simple means for regulating the direct current voltage output of a radio frequency high voltage power supply.

In my invention a high frequency voltage is generated by exciting a quarter-wave coaxial line, closed at one end and open at the opposite end. Coupled to the open end is a diode rectifier device which rectifies the high frequency voltage, the rectified voltage being directed to a load. Regulation is obtained by operating the diode rectifier device emission limited and controlling its filament current through a circuit responsive to changes in output voltage.

The novel features which I believe to be char acteristic of my invention are set forth with particularity in the appended claims. My invention itself, however, both as to its organization and method of operation, together with further objects and advantages thereof may best be understood by reference to the following description taken in connection with the accompanying drawing in which is shown a diagram of a regulated high voltage direct current power supply in accord with my invention. v

Referring now to the drawing, an oscillator electron discharge device I is coupled to aresonant coaxial line 2 in a manner to excite and sustain oscillations in the line. The control electrode 3 of discharge device I is connected by a control electrode leak resistor l and capacitor 5 to a point on the outer conductor 6 of the coaxial line 2 near the short circuited or closed end I thereof. The center conductor 8 of the coaxial line is connected to the conductive closure member at the end I and is thereby short ci'rcuited to the outer conductor 6 at this end. The center conductor 8 of the concentric line may comprise a tubular or cylindrical member with an internal conductor as later described. Cathode 9 of the discharge device I is directly connected to the center conductor 8 near end I and anode III is connected through direct current blocking capacitor II at a point a short distance further along the line. Connections to the center conductor 8 are conveniently made through small openings 6' prov ded in outer conductor I; for the passage of the necessary wires or other conductive members as shown in the drawing. It will be recognized that elements I5 and 8 are preferably coaxial hollow cylinders, although other types of construction may be employed. Anode operating potential from a source indicated as B+ on the drawing is supplied to discharge device I through a radio frequency impedance element I2 which may comprise a choke coil.

Under conditions which are well known in the art, as to the values of the circuit components and location of the connections from the discharge device to the resonant line 2, device I oscillates and line 2 operates as a tuned circuit at the frequency at which the line length is onequarter of the wavelength. A high voltage of high frequency then exists between the inner and outer conductors 8 and 6 at the open end I3 of the line. The magnitude of this voltage is determined by the intensity of the oscillations in device I, by the relation between the distances from the closed end I to the points of connection to device I and by the distance from end I to end I3. Employing a 3+ source of 350 volts and a line length of 0.25 meter, for oscillations of 200 megacycles, the voltage at the end I3 of the line may be of the order of 10 kilovolts.

A diode'electron discharge device It is connected to rectify the alternating voltage at end I3 of the line, the anode I5 being connected through a filter capacitor I6 to the outer conductor and the filamentary cathode I'I being directly connected to the inner conductor 8. In order that the the filament of the diode may be excited from a source requiring only low voltage insulation, the inner conductor is conveniently formed of two .conductive members insulated from each other. As shown in the drawing, the inner conductor comprises a tubular member and a wire member I8 extending therethrough. Similar radio frequency voltages exist along both sections of the inner conductor 8, i. e. the tubular conductive-portion and the wire conductor I8. A'practical way of assuring that such voltages exist along wire member I8 is to situate by-pass capacitors I8 at both ends of member I8 as shown. Insofar as radio frequencies are concerned, accordingly, both of these portions may be considered as an inner conductor 8 for the resonant coaxial line.

The wire member I8 is brought out through a small opening 1 in the plate closing end 1 of the resonant line and a filament transformer secondary winding I9 is connected between this wire conductor and a portion of the end plate closely adjacent the small opening. The end I of the auaess The primary winding II is connected in series with a secondary winding 22 of a transformer 23. The primary winding ll of transformer 23 in series with a capacitor ll is connected for energimtion to a suitable source of alternating current, not shown, such as a conventional 60 cycle, 115 volt power source.

Transformer 23 comprises, in addition, a tertiary winding 2| through which a current may fiow under the control of electron discharge device 20. The current fiow through tertiary winding 2| serves to control the current fiow through filament ll since, as the current through winding II varies, the voltage drop across series capacitor 24' will vary thereby altering the voltage across primary winding 2|. As is well understood by those skilled in the art, the variation in the voltage of primary winding 24 will cause asimilar variation in the voltage of secondary winding 22, and consequently the current fiow through filament I! may be controlled. Suitable control may also be obtained by replacing series capacitor II with a resistor of adequate size.

The transformer tertiary winding 2F is center tapped and the center tap connected o the interconnected cathodes 21 and 28 of t 1 dual triode discharge device I. Cathodes 11 and 28 are connected to ground through a suitable source of direct current represented conventionally by battery 21'. The anodes I! and ll are respectively connected to opposite ends of the tertiary winding whereby each triode acts as a variable load across a respective half of the tertiary winding. The amount of loading thus imposed is under the control of the interconnected control electrodes 3| and 32 of the triode devices.. Control of the potential of the control electrodes with respect to cathodes 21 and 2. is provided by a direct current amplifier comprising an electron discharge device 33, of which the anode 34 is directly connected to control electrodes 3i and l! and through an anode resistor II to a source of operating potential indicated as 8+ on the drawing.

In operation, rectifier device It provides at its anode II a high negative potential with respect to ground by rectifying the radio frequency voltage at the end I3 of line 2. The value of the direct current voltage may be primarily determined by the emmissivity of the filamentary cathode ll of the rectifier ii if the resistance of a pair of resistors 31 and il, and the load resistance connected thereacross, are properly proportioned with respect to the power supply components. Assuming that a tap 39 has been set, by trial and error, at a point along resistor 38 such that a desired output potential is obtained, any reduction in the output potential will cause tap a to vary toward ground potential, or become less negative. Control electrode 40 of device 33, becoming less negative, increases the current fiow in resistor 35 and drives control electrodes II. 32 more negative, or less positive, with respect to cathodes 21, 28. The triode devices of twin triode device 20 draw less current from tertiary winding 25 of transformer 23 causing less voltage drop in the capacitor 24' in series with the primary winding 24, and a higher voltage is induced in secondary winding 22 to provide, through transformer windings II and II greater 4 excitation to filament l1 tending to increase the emissivity thereof and increase the output potential. Increase of output potential, of course, initiates compensation in the opposite sense .to reduce the emissivity of filament II.

To provide stability and rapid response the diode device II should be one embodying a tungsten filamentary cathode ll rather than one having an oxide coated filament or an indirectly heated cathode. While a tungsten filament is specified, other materials may be suitable, of course, but in general filaments or cathodes treated to decrease the work function tend toward instability or erratic characteristics when used in an emission limited system as in the present instance. Timgsten filaments have proven satisfactory in this type of service, sacrificing some efiiciency in favor of greater stability.

It is possible with properly designed diode devices, having filaments arranged for rapid temperature changes, to provide an overall system response to compensate for changes in output voltage within 0.5 second, and in the absence of rapid fluctuations in load current, or line voltages, the output potential is stabilized within a very narrow range of for example 0.1% in certain applications.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. A regulated high voltage direct current power supply comprising a quarter-wave coaxial resonant line, said line having an open end and an opposed short circuited closed end, an oscillator for exciting said line coupled thereto adjacent said closed end, a rectifier having an anode capacitively coupled to the outer conductor of said line at said open end and a filamentary cathode, the inner conductor of said line comprising two conductive members insulated from each other and each extending throughout the operative length of said inner conductor, said filamentary cathode being connected between said members at said open end, an impedance connected from said anode to said closed end of said line across which the direct current output voltage appears, and means responsive to the voltage across a portion of said impedance for supp y g heating current to said filamentary cathode through said members controlled to maintain constant the voltage across said portion of said impedance, whereby said output voltage is maintained constant.

2. A regulated high voltage direct current power supply comprising a quarter-wave coaxial resonant line, said line having an open end and an opposed short circuited closed end, an oscillator for exciting said line coupled thereto ad- Jacent said closed end, a rectifier having an anode capacitively coupled to the outer conductor of said line at said open end and a filamentary cathode, the inner conductor of said line including a tubular conductive member and a wire member disposed in insulating relationship within said tubular member, said filamentary cathode being connected between said members at the open end of said line, an impedance connected from said anode to said closed end of said line across which the direct current output voltage appears. and a source of alternating current for supplying heating current to said filamentary cathode, said source being connected between said members at the closed end of said line through a circuit responsive to the voltage across a portion of said impedance whereby the current 5 V in said filamentary cathode is controlled and said output voltage is maintained constant.

3. A regulated high voltage direct current power supply comprising a quarter-wave coaxial line having an open end and an opposed short circuited closed end, an oscillator for exciting said line coupled thereto adjacent said closed end whereby a high voltage of high frequency appears at the open end of said line, a rectifier having an anode capacitively coupled to the outer conductor of said line adjacent said open end and a filamentary cathode, the inner conductor of said line including a tubular conductive member having a wire member disposed in insulating relationship therewithin and extending throughout the operative length of said inner 6 conductor, said filamentary cathode being connected between said members adjacent the open end of said line, an impedance connected from said anode to said closed end of said line across which the direct current output voltage appears, and a source of alternating current for supplying heating current to said filamentary cathode,

said source being connected between said members at the closed end of said line through a circuit responsive to the voltage across a portion of said impedance whereby the current in said filamentary cathode is controlled and said output voltage is maintained constant. 4

ALEXANDER, E. HUDSON,

No references cited. 

